A number of patents and publications are cited herein in order to more fully describe and disclose the invention and the state of the art to which the invention pertains. Each of these references is incorporated herein by reference in its entirety into the present disclosure, to the same extent as if each individual reference was specifically and individually indicated to be incorporated by reference.
Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise,” and variations such as “comprises” and “comprising,” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.
It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a pharmaceutical carrier” includes mixtures of two or more such carriers, and the like.
Ranges are often expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment.
This disclosure includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
Rheumatoid Arthritis
Rheumatoid arthritis (RA) is a chronic inflammatory disease characterised by painful swelling, stiffness, loss of movement and the destruction of cartilage and bone. RA is characterised by an inflammation of the synovial lining of multiple joints and commonly affects the joints of the wrist and hands and may also affect the elbows, shoulders, hips, neck and knees; the ultimate hallmark of RA is joint destruction. RA is a common disease, estimated to affect up to 1% of adults in the developed world, with women more than twice as likely to be affected and over 30% of patients likely to become severely disabled within 20 years (see, e.g., Feldmann et al., 2006). RA is one of the most important causes of disability in the western world and is associated with a significant reduction in quality of life as well as increased mortality if left untreated. The disease can start at any age, with individuals aged between 40 and 70 most commonly affected.
The exact cause of RA remains unclear, but is highly complex and may involve the combination of a number of factors which lead to the development of autoantibodies, formation of immune complexes, production of pro-inflammatory cytokines, angiogenesis and eventual bone and cartilage loss (see, e.g., Klareskog et al, 2006; Ziff et al, 1990; Weissmann et al, 2006; Firestein et al, 2005). These factors include an abnormal immune response caused by reduced self tolerance or a biological trigger such as reaction to environmental factors, infectious agents, or hormonal stimulus (see, e.g., Klareskog et al, 2006); antibodies to the Fc fragment of IgG, known as rheumatoid factor, are present in 60-80% of adults with RA (see, e.g., Weissmann et al, 2006) but it is not known whether this is factor is responsible for initiating the inflammatory cascade or are generated at a later stage and propagate the process (see, e.g., Weissmann et al, 2006); there is also a notable genetic predisposition to the disease, as shown by the presence of HLA-DR4 antibody in 70% of patients (see, e.g., Klareskog et al, 2006).
At the cellular level, development of RA usually commences with T-cells infiltrating the synovial membrane lining the affected joint; this then leads to the activation of macrophages, monocytes and synovial fibroblasts (see, e.g., Firestein, 1996) by way of cell-cell contact and release of various cytokines, including TNFα and IL-1 (see, e.g., Feldmann, 1996). Activation of these cells leads to the overproduction of a range of pro-inflammatory cytokines of which the most important are TNFα, IL-1 and IL-6 (see, e.g., Brennan et al, 1996; McInnes et al, 2005). These pro-inflammatory cytokines are then instrumental in orchestrating several complex signal transduction cascades, including the NFκB, MAPK and Jak/STAT pathways (see, e.g., Firestein et al, 1999) which lead to the induction of genes coding for various products which propagate the inflammatory response and also promote tissue destruction. These products include tissue degrading enzymes such as collagenases, matrix metalloproteases, cathepsins, and other pro-inflammatory factors such as selectins, integrins, leukotrienes, prostaglandins, chemokines, and other cytokines. Furthermore, TNFα and IL-1 also induce RANKL expression.
RANKL is an essential factor for the generation of osteoclasts (see, e.g., Tanaka et al, 2003; Roodman, 2006), and upregulated RANKL-production leads to increased osteoclasts differentiation and ultimately bone destruction (see, e.g., Tanaka et al, 2003; Roodman, 2006). The inflammatory response leads to the accumulation of many leukocytes and immune factors populations within the affected joint and also to hyperplasia of the Type-A and Type-B synovicytes (see, e.g., Firestein et al, 2005), leading to thickening and vascularisation of the synovium into a destructive and aggressive tissue known as a pannus. The pannus contains both osteoclasts which destroy bone, and metalloproteases which continue the destruction of cartilage.
Treatment of Rheumatoid Arthritis
Early therapies for RA focussed on controlling the symptoms of the disease, mainly by reduction of inflammation, rather than retarding disease progression. These drugs included NSAIDs such as aspirin, diclofenac and naproxen and, until recently, the COX-2 selective drugs Celebrex® and Vioxx® were also widely used. Inflammation was further controlled by glucocorticoids, and their combination with NSAIDs provided reasonably effective short-term control of the inflammation. More recently, a more aggressive approach to treating RA has been introduced starting at disease onset, using so-called disease-modifying anti-rheumatic drugs (DMARDs) which act to slow or even prevent disease progression. These include a number of older drugs, including gold salts; sulfasalazine; antimalarials such as hydroxychloroquine; D-penicillamine; immunosuppressants such as mycophenolic acid, azathioprine, cyclosporine A, tacrolimus and sirolimus; minocycline; leflunomide; and most importantly, methotrexate (see, e.g., Smolen et al, 2003).
Methotrexate is now the gold-standard therapy for clinical trial comparisons, and is generally used in combination with newer therapies. It is effective in most patients but, in common with all of the above agents, has significant gastrointestinal side effects which lead to roughly 50% of patients eventually having to cease treatment with methotrexate (see, e.g., Mount et al, 2005). A further drawback of these older DMARDs is the length of time taken for the drug to start acting, ranging from weeks with methoxtrexate, to months with gold salts. Whilst full remissions only occur in about a quarter of patients, for those showing no effect it is not generally possible to stop therapy without suffering the risk of a more violent disease rebound (see, e.g., Smolen et al, 2003). In recent years, the treatment of RA has been revolutionised by the advent of biological agents which target specific inflammatory pathways. The first and most important of these are the anti-tumour necrosis factor (anti-TNF) agents (see, e.g., Elliott et al, 1994).
The Role of TNFα in RA
As discussed above, the TNF superfamily of receptors and ligands plays a key role in the causation of inflammation and associated local and systemic bone loss. TNFα production within the joint may in fact play the pivotal role in orchestrating the production of other factors which leads to the persistence of inflammation and tissue damage (see, e.g., Feldmann et al, 2001; Brennan et al, 1999; Brennan, 1992). The importance of TNFα in RA is highlighted by the finding that antibodies blocking TNF can prevent inflammation in animal models of RA, and that anti-TNF therapy is currently the most effective treatment for RA (see, e.g., Elliott et al, 1994; Feldmann et al, 1994; Joosten et al 1996, Klareskog et al, 2006). However, there is evidence that there are some TNF-independent effects of IL-1 in RA, most notably bone destruction (see, e.g., van den Berg et al, 1999; van den Berg et al, 2002).
TNF is a cytokine that affects many different functions, including the alteration of tissue remodelling, changes to the permeability of the epithelial cell barrier, activation of macrophages, up-regulation of adhesion molecules, recruitment of other immune response effectors and, most importantly in RA, it instigates the signalling cascade which leads to the activation of the transcription factors NFκB and AP-1 (see, e.g., Liu, 2005; Baud et al, 1999). Binding of TNF and IL-1 to their respective receptors leads to the recruitment of downstream signal transducers called TRAFs. Further kinases are recruited by the TRAFs, and the resulting kinase complex activates the Map-kinase pathway, ultimately leading to activation of AP-1, and the phosphorylation of IκB kinase. IκB is the inhibitor of NFκB, which acts by preventing translocation of NFκB to the nucleus. Phosphorylation of IκB by IκB kinase leads to degradation of IκB. Once IκB has been degraded, NFκB migrates to the nucleus, where it promotes transcription of anti-apoptotic genes, which promote survival of T and B-cells, thereby prolonging the immune response. This prolongation of the inflammatory response is central to the chronic nature of RA. The importance of NFκB activation is demonstrated by the fact that inhibition of NFκB activity by inhibitory peptides can prevent arthritis in animal models of RA (see, e.g., Jimi et al, 2004).
Anti-TNFα Therapy
Anti-TNFα therapy represents the market-leading therapies for RA, and is performed either with neutralising antibodies such as infliximab (Remicade® J&J and Schering Plough) and adalimumab (Humira®, Abbott) or decoy receptors such as etanercept (Enbrel® Amgen and Wyeth), both which represent validated and highly effective treatments for RA. Anti-TNF biologicals are already licensed for RA, Crohn's disease, and psoriasis. A number of other inflammatory and autoimmune disorders are also being investigated as potential targets. Other approaches to blocking the action of TNF include the pegylated anti-TNF fragment certolizumab (Cimzia®, UCB); inhibition of proximal signalling intermediates such as MAP kinase; interference with the synthesis of TNF via inhibition of TNFα converting enzyme (TACE); and inhibition of the metalloproteases responsible for cleaving TNF from the cell surface (see, e.g., Smolen et al, 2003; Mount et al, 2005).
Other Inhibitors of NFκB Activation
As described above, the binding of IL-1 and RANKL to their receptors also initiates a signalling cascade, which eventually leads to the activation of NFκB and subsequent inflammatory response. The efficacy of inhibitors of these ligands has been validated by the use of the IL-1 receptor antagonist anakinra (Kineret® Amgen) for the treatment of RA, and the progression of the monoclonal antibody against RANKL AMG-162 (Denosumab® Amgen) through to phase III clinical trials for osteoporosis (it is also in clinical trials for RA and psoriasis).
Other Common Inflammatory Diseases Mediated by TNFα
There are several other common inflammatory diseases in which TNFα has been shown to play a major role and in which TNFα inhibitors have found therapeutic use. These include inflammatory bowel disease (IBD) and psoriasis.
IBD is an inflammatory disorder of the gut affecting about 0.25% of the population in the western world, of which the two main forms are: ulcerative colitis (UC), in which the lining of the colon becomes inflamed and ulcerated; and Crohn's disease (CD), which can occur anywhere within the gastrointestinal tract, but most often the ileum, and commonly involves inflammation of the entire gut wall. Common symptoms of IBD are bloody diarrhea and abdominal pain.
Psoriasis is an inflammatory response of the skin affecting 1-3% of the population in the western world. The disease is characterised by raised, red, scaly plaques on the skin, which may be itchy and also cause significant psychological distress by their unsightly nature. A further complication of psoriasis is the development of psoriatic arthritis, an inflammatory arthritis of the joints, in up to 40% of patients, which develops on average 10 years after the first symptoms of skin disease are seen (see, e.g., Gottlieb, 2005).
As with RA, the etiology of IBD and psoriasis are unknown and may involve a complex combination of infectious agents, environmental, and genetic factors, generating an inappropriate and prolonged inflammatory response.
Treatment of IBD and psoriasis has followed a similar pattern to that of RA, with the past use of immunoregulatory agents such as NSAIDs, methotrexate, cyclosporine, steroids, and antimetabolites such as 6-mercaptopurine for IBD (see, e.g., Korzenik et al, 2006) and methotrexate and cyclosporine for psoriasis (see, e.g., Gottlieb, 2005). The treatment of both has been revolutionised by the advent of biological agents, in particular those which block TNFα signalling. Etanercept is licensed for the treatment of psoriasis and psoriatic arthritis; both infliximab and adalimumab are licensed for psoriatic arthritis and IBD and are in late stage clinical trials for psoriasis.
Common Bone Diseases
Osteoporosis is a common disease characterised by reduced bone density, deterioration of bone tissue, and an increased risk of fracture. Many factors contribute to the pathogenesis of osteoporosis including poor diet, lack of exercise, smoking, and excessive alcohol intake. Osteoporosis may also arise in association with inflammatory diseases such as rheumatoid arthritis, endocrine diseases such as thyrotoxicosis, and with certain drug treatments such as treatment with glucocorticoids. However one of the most important factors in the pathogenesis of osteoporosis is heredity.
Paget's disease of bone is a common condition of unknown cause, characterised by increased bone turnover and disorganised bone remodelling, with areas of increased osteoclastic and osteoblast activity. Although Pagetic bone is often denser than normal, the abnormal architecture causes the bone to be mechanically weak, resulting in bone deformity and increased susceptibility to pathological fracture.
Bone involvement is a feature of many types of cancer. Cancer-associated bone disease can be manifest by the occurrence of hypercalcaemia or the development of osteolytic and/or ostesclerotic metastases. Increased osteoclastic bone resorption plays a key role in the pathogenesis of both conditions. Whilst almost any cancer can be complicated by bone metastases, the most common causes are multiple myeloma, breast carcinoma, and prostate carcinoma. The most common tumours associated with hypercalcaemia are multiple myeloma, breast carcinoma, and lung carcinoma.
RANKL signalling has been shown to play a major role in osteoclast over-activity and a consequent increase in bone loss (see, e.g., Tanaka et al, 2003; Roodman, 2006). The use of drugs which affect this pathway has been validated by the progression through to phase III/II clinical trials of the monoclonal antibody against RANKL AMG-162 (Denosumab® Amgen) for the treatment of osteoporosis/multiple myeloma.
As described previously, bone loss also plays a major role in the pathophysiology of rheumatoid arthritis and drugs which prevent activation of the signalling pathways described (e.g. TNFα blockers) are also able to prevent this bone loss.
Agents that Prevent Inflammation and/or Bone Loss
The inventors have identified a new class of compounds which, for example, prevent inflammation and/or bone loss, and thus may be used in the treatment of diseases with an inflammatory or autoimmune component, including, for example, rheumatoid arthritis, inflammatory bowel disease, psoriasis, and psoriatic arthritis; as well as diseases which involve bone loss, including, for example, bone loss associated with rheumatoid arthritis, osteoporosis, Paget's disease of bone, and multiple myeloma.
Without wishing to be bound by any particular theory, the inventors believe that this action may be via a mechanism that involves blocking TNFα and/or IL-1 and/or RANKL-signalling.
Biphenyl Ketones
Greig et al, 2003, describes a broad class of biphenyl ketones as anti-resorptive agents for the treatment of bone diseases. The present inventors have identified a much narrower subclass of biphenyl ketones, specifically, certain 2′,4′-dichloro-biphenyl-4-yl-hydroxy-ketones and related compounds, as defined herein, that have surprising and unexpected properties.
Specifically, the representative compound, 1-(2′,4′-dichloro-biphenyl-4-yl)-6-hydroxy-hexan-1-one (ABD328), is orally active, fully prevents bone loss in the mouse ovariectomy model, and also prevents inflammation in the collagen-induced arthritis model.
Consequently, compounds within the narrower subclass of biphenyl ketones described herein (and in particular, ABD328) have the potential to be orally active agents for the treatment of inflammatory diseases and/or for the treatment and/or prevention of bone loss.